It is now well understood and accepted that Vitamin B-12 is an important and central factor in many body functions. It is necessary for normal metabolism of nerve tissue and is involved in protein, fat and carbohydrate metabolism. Vitamin B-12 is required for the synthesis and transfer of single carbon units such as the methyl group, and aids in the synthesis of methionine and choline, which are important lipotrophic substances.
Among its other functions, Vitamin B-12 is required for the formation of red blood cells and increases tissue deposition of Vitamin A by improving either carotene absorption or its conversion to Vitamin A. Vitamin B-12 is also closely related to the actions of four amino acids, pantothenic acid, and Vitamin C, and plays a part in reproduction and lactation. Additionally, vitamin B-12 helps reduce the possibility of skin bruises and has been suggested as helpful in combatting alcoholism, diabetes mellitus, osteoarthritis, multiple sclerosis, certain mental diseases, and a number of other diseases and abnormalities.
Vitamin B-12, however, is a very complex vitamin. It contains an atom of cobalt in its center and is a charged molecule with a high molecular weight. The structure is similar to that of hemoglobin with iron at its center and to chlorophyll with a central magnesium atom. It cannot be made synthetically, but must be grown, like penicillin, in bacteria or molds. Animal protein is virtually the only source in which vitamin B-12 occurs naturally in substantial quantities. The human body cannot synthesize vitamin B-12, and consequently, it must be obtained externally if there is a deficiency, that is, by dietary intake.
The nature of vitamin B-12 is such that it is transported throughout the body by serum protein in the blood and is stored by many of the body tissues, especially the liver, kidney, stomach, muscle and brain. The liver is the primary storage site, and in good nutritional states, contains about 2 to 5 milligrams, which is considered sufficient to last the average human being from about 2 to 5 years.
For vitamin B-12 to be effective within the human body, a special system is necessary, since, due to its complex structure, it is unable to diffuse across cell membranes as are other vitamins. This special system is called the "intrinsic factor" and is a special protein secreted by the stomach. The intrinsic factor, by a mechanism not entirely understood, transports vitamin B-12 across the cell membrane in the wall of the small intestine, with the vitamin B-12 being released from the intrinsic factor and asorbed into the blood.
When the human body is healthy, the amount of vitamin B-12 ordinarily absorbed into the blood by the intrinsic factor is about 2.5 to 3 micrograms per day. However, when the human body is not healthy and is suffering from pernicious anemia, for example, the intrinsic factor is lacking, and consequently, the body does not absorb adequate amounts of vitamin B-12. The vitamin B-12 deficiency manifests itself in human beings, most commonly, in motor and mental difficulties. The symtoms are rapid heartbeat, cardiac pain, shortness of breath, edema of the face, general jaundice and intense brown discoloration around the small joints, weakness and fatigue. Neurological changes, such as peripheral neuritis, spinal cord changes, intermittent numbness and tinglings in arms and legs, diminished tendon reflexes, unsteady gait, etc. may also occur.
To overcome such deficiency, however, is extremely difficult since vitamin B-12 does not become absorbed into the blood to any significant extent when taken orally, regardless of the amount. Thus, as reported by H. Berlin et al, Acta Med. Scand. 184 247-258, 1968, and H. Hedstrand, Acta Med. Scand. 186 535-537, 1969, only approximately 1.2% of oral vitamin B-12 is absorbed over rather a wide range and such absorption rate is not dependent on the presence of the intrinsic factor. Moreover, even insofar as the absorption of such a small quantity is concerned, there may be significant limitations such as a lack of hydrochloric acid, a lack of animal protein intake, or other gastro intestinal problems which create poor absorption capabilities.
Because of the extremely limited ability of vitamin B-12 to be absorbed into the blood when taken orally, in the past, the treatment process has had to be in the form of vitamin B-12 injections. Such injections, however, have a number of significant drawbacks. First, injections are objectionable to administer because of the pain associated therewith. In this same regard, to many, the idea of injection treatments is inherently objectionable and offensive, and, consequently, there is a tendency not to proceed with the treatment. Additionally, as with any injection treatment process, needle abscess may occur and the treatment process is expensive. Finally, in the treatment of persons addicted to narcotics, with which pernicious anemia is often associated, treatment by injection has clear limitations.